1. Field of the Invention
The present invention relates to a magnetic head device for use in floppy disk devices or the like.
2. Description of the Related Art
In a magnetic recording method in which a leakage flux from a magnetic recording medium is introduced from a gap into a magnetic head including a coil for a readback process, a magnetic flux is also introduced into a magnetic head core due to an external magnetic field from a motor, a power supply or the like, and noise may be generated by the magnetic flux causing errors.
To cope with the above noise, there are provided various types of magnetic head devices in which a shield ring (shield portion) made of a magnetic material such as ferrite or permalloy is disposed at an outer circumference of a magnetic head core in order to guide magnetic fluxes from external magnetic fields into the shield ring thereby preventing the magnetic fluxes from going into the magnetic head core.
As one example of the aforesaid type of magnetic head devices, there is a magnetic head device in which a magnetic head core, a slider, and a coil wound on a bobbin are disposed in a shield ring, a terminal block having terminal pins to which lead wires of the coil are connected is formed integrally with the bobbin at one end of a narrow extension whose width is smaller than the width of a flange of the bobbin, the narrow extension of the bobbin fits in a slit of the shield ring to thereby allow the terminal block to be disposed outside the shield ring, and the slit of the shield ring is kept to a minimum size required to eliminate the influence of external noise.
As one example of a bobbin and a terminal block integrated with the bobbin for use in such a magnetic head device as described above (hereinafter referred to as xe2x80x9cintegration bobbinxe2x80x9d), the inventor of this application disclosed an integration bobbin in Japanese Patent Application Laid-open No. Hei 11-53707. The integration bobbin will be described with reference to FIG. 7.
In FIG. 7, lead wires 53 from a coil 52 on a bobbin proper 51 of the integration bobbin 50 are guided toward a terminal block 56 passing over a narrow extension 55 extending from a bobbin flange 54 formed at one end of the bobbin proper 51. The bobbin flange 54, the narrow extension 55 and the terminal block 56 are integrally formed. The width of the narrow extension 55 is made slightly larger than the width of a slit (opening portion) in a shield ring (not shown).
A projection 57 is provided on the terminal block 56 for guiding the lead wires 53. The lead wires 53 from the coil 52 are bound on respective terminal pins 58a to 58c by way of the projection 57.
In recent years, magnetic disk devices tend to become higher in density and smaller in size, and in association with this tendency magnetic head devices for use in the magnetic disk devices have been also made smaller and thinner. In addition, the magnetic head devices are required to be constructed to allow a certain tolerance in dimensions in consideration of variance in assembly and components.
However, in the prior art shown in FIG. 7, the projection 57 is provided on the terminal block 56, which increases the longitudinal dimension of the magnetic head device, whereby a tolerance in dimension relative to a shutter of a floppy disk is reduced. Thus, depending on an accuracy of assembling magnetic head devices, there may be a risk such that the floppy disk and the projection 57 on the terminal block 56 are in contact with each other causing scratches or damages to magnetic heads of the magnetic head device or the floppy disk.
The present invention has been made in light of the above, and it is an object of the present invention to provide a magnetic head device which can achieve the same effect as the prior art devices without providing a projection for guiding lead wires.
According to a first aspect of the present invention, in a magnetic head device in which a shield ring comprises a magnetic head core, a slider and a coil wound on a bobbin, one flange of the bobbin extends (flange extension) in one direction for a predetermined length maintaining its width, a narrow extension having a smaller width than the flange extension is formed integrally on an end face of the flange extension, a terminal block having terminal pins to which lead wires of the coil are connected is formed integrally at an end of the narrow extension and in which the narrow extension of the bobbin fits in a slit provided in the shield ring making the terminal block to be positioned outside the shield ring, a guide recess for guiding the lead wires of the coil is formed on a distal end of the terminal block, and the lead wires are connected to the terminal pins through the recess.
According to a second aspect of the present invention, in the first aspect of the invention, the terminal block is of a substantially rectangular shape, the guide recess is formed on a face of the distal end of the terminal block away from the narrow extension, and the terminal pins are provided on a lower face of the terminal block, which is present on a side of an outward face of the one flange opposite to a face in contact with the coil.
According to a third aspect of the invention, in the second aspect of the invention, the narrow extension is formed such that one side thereof is recessed from one side of the flange extension thereby defining a cutout while another side thereof is flush with another side of the flange extension, and an angle xcex8 formed between the one side of the flange extension and a line segment connecting a point defined by a side line of another flange in line with the one side of the flange extension intersecting with an end line of the another flange positioned toward the terminal block and a point defined by a bottom corner of an inlet of the guide recess toward the cutout is set to meet xcex8 greater than tanxe2x88x921(b/a) where a is a length of the flange extension and b is a depth of the cutout.
According to a fourth aspect of the present invention, in any of the first to third aspects of the invention, the depth of the guide recess ranges from 0.1 mm to 0.5 mm.
According to a fifth aspect of the present invention, in any of the first to third aspects of the invention, the depth of the guide recess gradually decreases from the inlet for lead wires toward the terminal pins.
According to a sixth aspect of the present invention, in any of the first to fifth aspects of the invention, the width of the guide recess is small at the inlet on a lead wire introduction side of the guide recess and gradually increases toward the terminal pins.